Appendix 1 is a computer program listing which is submitted on one compact disc that is referenced and incorporated herein by reference. Appendix 1 comprises a single file, Aomrtd, which was created on Oct. 25, 2001 and includes 26.2 KB.
The present invention generally relates to a system and method for determining the minimum resolvable temperature difference of a thermal imager. Trained human operators currently measure minimum resolvable temperature differences (MRTDs). The equipment used to measure MRTDs generally includes a black body thermal energy source, a collimator, a series of masks in which a four bar pattern has been milled and the thermal imager being tested. The width of and spacing between the bars of the mask varies between masks. The output of the black body passes through the slits in the mask and are collimated by the collimator. The thermal imager images the mask. The temperature difference between the mask and thermal energy source creates an intensity difference. The temperature of the black body thermal energy source is raised above ambient temperature to produce a bright four-bar pattern on the thermal imager. The human operator lowers the temperature of the black body until the four-bar pattern is no longer observed. The difference between the temperature of the thermal energy source and ambient background temperature is the MRTD for that particular bar pattern. A new bar pattern then is inserted and the procedure is repeated. When the test is completed, a plot generally is made of the MRTD vs. the width of the bars. This type of test is time consuming and expensive. Moreover, the results are highly subjective and not readily repeatable. A further shortcoming of determining MRTDs using standard test methods is that the results are not applicable to performance automated target detection computer algorithms.
Therefore, a need exists for an automated system for determining MRTDs that provides standardized, objective, and repeatable results.
The present invention provides an automated system that determines the minimum resolvable temperature difference of a thermal imager source with respect to a background scene. The system comprises: a) a thermal energy for generating thermal signals; b) at least one pattern mask for transforming the thermal signals into thermal image signals; c) a thermal imager for detecting and transforming the thermal image signals into transformed signals; and d) a computer for determining the minimum resolvable temperature difference of the thermal imager from the transformed signals. A display coupled to the computer may be used to present the minimum resolvable temperature difference in human readable form.
The invention may also be characterized as a method for determining the minimum resolvable temperature difference of a thermal imager with respect to a background scene. The method includes the steps of: a) generating a series of thermal signals; b) transforming the thermal signals into thermal image signals; c) transforming the thermal image signals into transformed signals; and d) determining a minimum resolvable temperature difference of a thermal imager from the transformed signals.
The invention provides repeatable results for determining MRTDs of the same as well as different types of sensor arrays. The use of the invention makes performance comparisons of such sensors more meaningful by eliminating interpretation of results by human operators. These and other advantages of the invention will become more apparent upon review of the accompanying drawings and specification, including the claims.